Eversource Energy officials said Friday the company has told state utility regulators it will seek a natural gas service rate hike that, if approved, would increase customer bills by an average of 15.8 percent over a three-year period.

The company filed a notice of intent with the Public Utilities Regulatory Authority on Friday announcing its plans to seek the rate increase. Bill Akley, president of gas operations for Hartford-based Eversource, said the increased revenue is needed so the company can continue upgrading its distribution network.

Eversource customers would see a 9.2 percent average increase in their natural gas bills in the first year of the plan proposed by the utility. Customer bills would increase by an average 3.7 percent during the second year of the proposed rate hike followed by a hike of 2.9 percent in the third year.

If approved, the first of the rate increases would begin on Jan. 1, according to Eversource officials.

Eversource has 3,370 miles of natural gas infrastructure in 73 communities around the state and has replaced 145 miles of gas pipelines since 2011. The company plans to upgrade an additional 371 miles natural pipeline over the three-year period covered in the filing, said Tricia Taskey Modifica, a company spokeswoman.

The proposed upgrades include replacing existing cast iron and bare steel gas main with newer plastic pipe that company officials say is safer, more durable and is better able to deal with fluctuating underground temperatures.

“These investments allow us to enhance safety and further modernize the gas distribution system, minimizing repairs and any service interruptions, to ensure our customers have energy for every moment of their lives,” Akley said in statement. “Each mile of leak-prone main we replace makes our gas system safer, stronger and helps the environment.”

Friday’s notice of intent will be followed with a more detailed rate increase filing within 30 days to 60 days, according to company officials. Eversource officials stressed that the percentage increases are based on averages and the amount that customers’ bills increase could be lower or higher.

Lauren Bidra, an attorney with the state’s Office of Consumer Counsel, said agency officials “are concerned with the magnitude of the requested rate increase.” The OCC represents the interests of consumers in utility rate cases.